A man in Seoul, South Korea, watches a news broadcast of North Korea's nuclear test at Seoul Station on Jan. 6, 2015. North Korea's warheads — at least 20 in number, and perhaps as many as 60 — remain for now in their bunkers, somewhere in the rugged hills north of Pyongyang.

The warheads — at least 20 in number, and perhaps as many as 60 — remain for now in their bunkers, somewhere in the rugged hills north of Pyongyang. Until today, there has been no public pledge from North Korea to dismantle them, or to allow inspectors to see them, or even to disclose where they are kept.

Work continues daily in the country's radiochemistry lab near Yongbyon, where plutonium for new bombs is extracted from spent fuel rods. Just across a small river from the lab, testing continues on a 20-megawatt reactor capable of producing nuclear fuel for scores of additional bombs.

The facilities are among hundreds that exist across a North Korean weapons complex that has shown itself capable not only of making sophisticated nuclear and chemical weapons, but also of expertly hiding them from public view. It is why weapons experts around the world expressed astonishment Wednesday at President Donald Trump's claim that the danger posed by Pyongyang's decades-long weapons buildup had been effectively eliminated — that there was, as Trump wrote in a Twitter posting, "no longer a nuclear threat from North Korea."

While the U.S.-North Korean summit may have lessened the immediate risk of a war, the elimination of the North Korean threat is at best a distant prospect, according to weapons experts and veterans of past negotiations with Pyongyang. Such an achievement would require difficult negotiations, years of dismantling and verification, and — perhaps most important - a profound change in the behavior of a state with a long history of cheating and deception on its past commitments, analysts said.

Hours after Trump's declaration of victory at the Singapore summit, some derided the notion of a suddenly defanged North Korea as naive and perhaps even delusional.

"North Korea's capabilities today are no different than they were a week ago," said Robert Einhorn, a Brookings Institution scholar and formerly a State Department arms-control official under Republican and Democratic administrations. Einhorn, who sat across the table from North Korean negotiators during previous talks on restraining the country's missiles program, said the elimination of the North Korean nuclear threat had occurred so far only within a "parallel universe" inside the president's mind.

"It is ludicrous that he doesn't recognize the situation," Einhorn said. "To him, somehow, not only have North Korea's intentions changed, but its capabilities are going away. I think he's naive on the intentions, and he's wrong about the capabilities."

North Korea's only public pledge so far regarding its nuclear arsenal is contained in a 19-word clause in the joint statement signed by leader Kim Jong Un during Tuesday's summit with Trump. In it, Kim vowed to "work towards complete denuclearization of the Korean Peninsula," a promise nearly identical to one that North Korean leaders made during previous international negotiations going back to the early 1990s. In that period, Pyongyang tested six nuclear devices and an even greater number of long-range missile designs, some of them capable of delivering warheads to targets as far away as Washington.

After Tuesday's summit, North Korea's state-run Korean Central News Agency said the country would "abide by the principle of step-by-step and simultaneous action" during talks aimed at achieving "peace, stability and denuclearization" of the entire Korean Peninsula. But the statement made no specific pledges about the destruction of existing weapons or the dismantling of the sprawling network of factories and laboratories for making new ones.

Secretary of State Mike Pompeo, in a news conference in South Korea, acknowledged that disarming North Korea could take years to accomplish. But he said negotiations to work out the details of the denuclearization program could begin as early as next week, and he hinted that some specifics had been agreed on, if not yet announced.

"There was a great deal of work done that is beyond what was seen in the final document," he said.

But many steps must taken before - or at least in parallel with — any physical destruction of bombs and missiles, weapons experts say. For starters, the hyper-secretive North Korean government must produce a verifiable inventory of what it has — from the nuclear reactors that can be easily seen on satellite images to the underground bunkers and tunnels where U.S. intelligence officials believe North Korea's most advanced weapons and research facilities are hidden.

After that, the world's most reclusive state must agree to allow hundreds of foreign experts into the country to inspect each building and storage depot in the declared inventory, and at the same to investigate dozens of suspicious sites that are not on the official list.

Those steps, when completed, would set the stage for the actual dismantlement, an arduous and technically demanding process that various studies have projected could taken between two and 15 years. There are hundreds of known facilities related to nuclear and chemicals weapons and advanced missile systems, scattered across nearly two dozen sites in the mountainous country the size of Pennsylvania.

While North Korean officials adopted a strikingly positive tone in the run-up to this week's presidential summit, longtime North Korea observers have seen little evidence that Kim is preparing to take such dramatic steps. The only concrete moves toward disarmament were last month's destruction of the partially collapsed nuclear test site at Punggye-ri, and the apparent dismantling last week of one of the country's missile test stands.

Among veteran North Korea watchers, there remains deep skepticism that Kim will ever consent to giving up his entire nuclear arsenal, the singular asset that compelled a U.S. president to travel halfway around the world to meet the leader of one of the most world's most repressive and economically backward states.

"'Zero warheads' is not on the table as long as the Kim family rules in Pyongyang," said Robert Litwak, a North Korea expert and senior vice president of the Woodrow Wilson International Center for Scholars, a Washington think tank. "Their long game is not to lose the short game — and that means everything they do can be viewed through the prism of regime survival."

Other experts acknowledged that the summit probably did succeed in reducing the danger to Americans, at least for now, by diminishing the chance of a nuclear exchange with the United States. Jon Wolfsthal, an adviser on North Korea in the Obama administration's National Security Council, said the coming months could yet prove that Trump's unconventional approach to arms control was more successful than the efforts of his predecessors, at least in achieving a diplomatic detente with the notoriously belligerent North.

"The hesitation you hear in the voices of experts is, there's a small chance that this time is different," said Wolfsthal, now director of the Washington-based Nuclear Crisis Group. "On the other hand, we've been doing this dance with North Korea for 25 to 30 years. They've achieved a lot because of their nuclear program. It could be possible that they're going to give some of it up, but it's not going to happen in the blink of an eye."